Why has the glass cracked on my woodburner?

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There are several reasons why the glass might have cracked on a wood-burning stove, but all of the many reasons can be separated into two main causes:

  • Impact
  • Usage

Let’s explore both of those groups in more detail.

Impact

As you might have guessed, impact damage to your stove glass is caused by something coming into contact with your glass more forcefully than it should. The most common examples of this are:

  • Overloading the firebox with fuel, then inadvertently closing the door onto a protruding log.
  • Hitting the glass from the outside. For instance, banging the hoover into it or dropping/throwing something that hits the glass.
  • Over-tightening screws and bolts holding the glass in place. The impact of an overtightened screw can cause the glass to crack, especially once the stove is up to temperature and the glass expands slightly.

Keep in mind that, even though you might not see the crack straight away, it is possible that the glass is weakened or that a hairline crack that is not yet visible to the naked eye has been caused. Once the stove is operating at a high temperature, the crack might worsen.

Usage

Cracks that are caused by usage or, perhaps more accurately, misusage are those that are due to the way that the stove was being operated. Some of the main causes of misusage causing stove glass to crack are:

  • Overfiring. This is when the stove is being operated at too hot a temperature. This could be because there is too much fuel in the stove or because too much oxygen is being allowed into the firebox. Ironically, once the glass is cracked, extra oxygen inevitably gets into the stove, which causes even more overfiring. That’s why it is important to replace your stove glass when you first notice a crack.
  • Burning household coal. Standard household coal is fine to burn on open fires, but it is quite a volatile fuel. Within the confined space of a stove, this can lead to mini-explosions, which are forceful enough to crack the glass. Find out more about why your shouldn’t burn household coal on a stove.
  • Burning pet coke. Burning petroleum-based fuels – whether deliberately or because your fuel supply has because mixed with pet coke – is also likely to cause explosions in the firebox than will cause the stove glass to break.

Avoiding cracked stove glass

The best way to ensure you don’t crack the glass on your wood-burning stove is to take care when adding fuel, only burn the required amount and only burn the types of fuel recommended in your stove manual.

If the glass on your stove is currently cracked, the good news is that it is relatively inexpensive and quite easy to replace.

Find replacement glass for your woodburner now.

11 thoughts on “Why has the glass cracked on my woodburner?

    • Hi Gary

      Has it always been like that? It’s possible that there is a hairline fracture in the glass that’s gradually getting worse.

      Feel free to post a photo to our Facebook page.

      Thanks,

      Gr8Fires

  1. the glass in my log burner exploded and glass hit the fire gaurd we had put old Xmas cards and some sticks in to get it going and it did, iv No idea how it happened and its put me off using ever again I have three young children one was sat right in front of it thank god i had a really good fire gaude, should I replace the glass and carry on or get someone to check the log burner before I use it again feel sick over it the bang was so loud and the what IFs are playing on my mind thank you

    • Hi,

      It’s highly likely to be something to do with the operation of the stove, but obviously you don’t want it happening again so you need to get to the bottom of what caused it.

      Were any of the things mentioned in the article above applicable? In particular, burning household coal can cause a fairly powerful explosion.

  2. Hi
    Thank you for getting back to me.
    We had put sticks in and fire lighters to start it off and there was left over coal in it and a log…. its the compressed coal its what I was told to burn on it. Never used household coal.
    I have now read you shouldn’t burn logs and coal. The log burner was in the house when I bought it and I can’t be sure of the age or condition of the glass.
    I have been reading a lot on multifuel burners

  3. Please help, I had a replacement glass fitted to my stove due to an issue with a fault in the black etching surrounding the viewing panel. The supplier decided to fit it not as per the original manufacturers method using different size fire rope and sticking it to the glass instead of the metal door frame.. It has now cracked after 3 months of use. The crack started from the top edge away from the viewing panel and fire and within a fixing capping. The supplier is refusing to inspect it or take any responsibility for this. Any advice please?

    • Hi Phil

      Short of legal action (not our area of expertise) or a complaint to a professional body (if your supplier is part of one) there’s probably not too much you can other than replace the glass again and make sure it is done properly this time.

      Thanks,

      Gr8Fires

  4. Hi there I have just had the glass cracked in the corner of my Jarrahdale wood fire.I rang up suppler who we got to put it in and they weren’t really interested in this.I also rang the perth office and they said that I can still use it until I get it fixed is this a good ideal.As the cause wasn’t wood failing against it because it was empty at the time and only ashes were left there from the night before.Nore has it been hit with anything please help.

    • Hi Deb

      Yes, the glass is counted as a consumable and so isn’t generally covered by warranties etc. The reason for that is that the way a stove is operated makes a big difference to how long it lasts. If you’re confident there has been no impact, it is likely to have been caused by one of the usage issues mentioned above.

      We’d recommend getting it replaced as soon as possible. And if you do choose to light it with the crack (we can’t see the size and scale of the crack, of course), we would recommend you have a working carbon monoxide alarm nearby.

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